Control and safety device for fourcycle internal combustion engines



Jan. 10, 1961 R ROSSGER 2,967,519

CONTROL AND SAFETY DEVICE FOR FOUR-CYCLE Filed Feb. 20, 1958 INTERNAL COMBUSTION ENGINES 3 Sheets-Sheet 1 INVENTOR Z3004- P'sssa-E Jan. 10, 1961 Filed Feb. 20, 1958 R'ROSSGER CONTROL AND SAFETY DEVICE FOR FOUR-CYCLE INTERNAL COMBUSTION ENGINES 3 Sheets-Sheet 3 0/4 Reissues M INVENTOR 0004; FOSSGQ? United States PatentfO CONTROL AND SAFETY DEVICE FOR FOUR CYCLE INTERNAL COMBUSTION ENGINES Rudolf Riissger, Pirna (Elbe), Germany, assignor to VEB Motorenwerk Cunewalde, Obercunewalde, Oberlausitz, Germany Filed Feb. 20, 1958, Ser. No. 716,317

8 Claims. (Cl. 123-90) The invention relates to a control and safety device for four-cycle internal combustion engines, and more particularly to a device which prevents compression of the cylinder contents in the cylinders of a four-cycle combustion engine equipped with starting cams for easier starting of cold engines when the pressure of the lubricating oil in the lubricating system is insufficient, is lacking or suddenly drops.

Adequate lubrication is necessary for safe operation of internal combustion engines, and four-cycle engines are, therefore, commonly equipped with forced-lubrication systems by which lubricating oil under pressure is supplied to all points of friction in the engine. Failure of the lubricating system can cause serious damage to the engine. Indicating oil pressure gauges are normally supplied but do not provide adequate safety since continuous inspection of the gauge is not always practical. When the pressure drop in the lubricating system is discovered and the engine is stopped, enough time may have elapsed to cause damage to the engine.

It was therefore recommended to provide a safety device which was responsive to the oil pressure in the lubrication system and which shifted the cam shaft after starting of the engine from the starting position to the operating position, and which permitted the cam shaft to return to the starting position under the pressure of a spring when the oil pressure in the lubricating system dropped, and then to prevent compression by opening of the intake valves (decompression position).

When applied to engines which are equipped with special starting devices for facilitating starting of a cold engine, this device of the prior art has a serious disadvantage. When the oil pressure drops, the cam shaft shifts first from the normal operating position into the starting position, and only thereafter into the decompression position. This arrangement may permit the engine to run for a substantial period with the cam shaft in the starting position and to suffer substantial damage during this period.

The object of the invention is the provision of a control and safety device which prevents starting of the engine at inadequate oil pressure while automatically controlling cam action during the starting period, and which stops the engine in the case of oil pressure failure without the valve cams passing through the starting position. V

In its more specific aspects the control and safety device of the invention comprises control means actuated by two pressure means, one of said pressure means preventing complete closing'of the exhaust valves of the engine by shifting a rocker shaft from an initial position or rest position into a starting position, and then. shifting the rocker shaft into operating position after starting, the other pressure means causing the rocker shaft to return to the initial position without passing through the starting position.

The exact nature of the invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawings in which:

Fig. l is a diagrammatic view in side elvation of an embodiment of the control and safety device of the invention in the decompression position,

Fig. 2 illustrates the device of Fig. 1 in the starting position,

Fig. 3 illustrates the device of Fig. 1 in the normal operating position after starting,

Fig. 4 illustrates the device of Fig. 1 ready to be shifted from the normal operating position into the decompression position,

Fig. 5 illustrates the device of Fig. 1 in an intermediate posit-on while being shifted from the normal operating position into the decompression position,

Fig. 6 shows a portion of the device of Fig. 1 in front elevation viewed in the direction of arrow VI in Fig. 4,

Fig. 7 shows a section of the device taken on the line VII-VII of Fig. 4,

Figs. la, 2a, 3a, 4a, and 5a are diagrammatic views in plan view of details of Figs. 1, 2, 3, 4, and 5, respectively.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 (which illustrates a preferred embodiment) a cam shaft 1 of a four-cycle internal combustion engine. The cam shaft carries a set of cams for each of the cylinders of the engine. The cams coordinated with the valves of a single cylinder only are shown for the sake of clarity. An intake cam 5 and a starting cam 6 which are fixedly mounted on cam shaft 1 adjacent each other are capable of operatively connecting with push rod 18 which actuates the intake valve of the engine cylinder in a wellknown manner. Exhaust cam 7, the axial length of wh'ch corresponds approximately to the combined axial length of cams 5 and 6, cooperates with exhaust push rod 16 for actuating the exhaust valve of the engine cylinder. A rocker shaft 2 is slidably supported in the engine and has rocker arms 3 pivotally but not axially slidably mounted thereon. As best seen in Fig. 7, rocker arms 3 are fixedly connected with valve lifters or tappets 21 which are in sliding contact with the cams of cam shaft 1. A compression spring 4 urges rocker shaft 2 from a position of engagement between valve lifter 21 and intake cam 5 into engagment of valve lifter 21 with starting cam 6. A cone 15 and a collar 14 which projects over the base of cone 15 are mounted fixedly and coaxially on the end of rocker shaft 2 removed from spring 4. The height of cone 15 is approximately equal to the center-to-center distance of cams 5 and 6. Cone 15 and collar 14 are urged by spring 4 towards arm 8b of two-armed lever 8 which is fastened to pin 9. Pin 9 is slidably and rotatably mounted on the engine. The other arm 8a of lever 8 presses against a pin 12 which is slidably mounted in the engine and which presses one arm of two-armed lever 13 towards push rod 16 of the exhaust valve of the engine against the restraint ofa plunger 11. The plunger 11 is slidably mounted in a cylinder and is urged in the direction of the arrow against lever 13 by the pressure. of the oil in the lubricating system .which communicates with the cylinder in which piston 11 is reciprocably supported. The variable oil pressure on piston 11 and the fixed pressure exerted by the force of spring 4, therefore, tend to move shaft 2 with collar 14 and cone 15, lever 8, pin 12, and lever 13 in opposite directions. A collar 17 fixedly mounted on exhaust-valve push rod16 is engaged by the lip 13:; of lever 13 when the force ,of the spring prevails.

. Fig. la shows in plan view one end of shaft 2'with collar 14 and cone 15 fixedly mounted thereon and the end of arm 8b of lever 8.

Figs. 2-5 and 2a-5a show the device of Figs. 1 and 1a in diiferent operating positions and a detailed description of the individual elements illustrated is therefore not deemed required.

Fig. 6 shows a portion of the device of Fig. l in front elevation viewed in the direction of arrow VI in Fig. 4. Shaft 9 carries the arms 8a and 8b of two-armed lever 8. It is manually shiftable by means of hand lever 19. Arm 8b is positioned for cooperation with collar 14 and cone 15, and arm 8a is in operative contact with pin 12.

Fig. 7 is a section of the device of Fig. 1 taken on line VII-VII of Fig. 4. It shows cam shaft 1, rocker shaft 2, rocker arm 3, exhaust cam 7, and exhaust-valve push rod 16 actuated by valve lifter 21 and carrying fixed collar 17.

The illustrated device operates as follows:

With the motor standing still or with the oil pressure being low for any reason, the control and safety device of the invention may be manually pushed by lever 19 into the position illustrated in Fig. 1. Regardless of the position of exhaust cam 7 and valve lifter 21, the push rod 16 is prevented from completely closing the exhaust valve of the engine by engagement of the lip 13a of lever 13 under collar 17 whereby the push rod 16 is raised out of contact with the valve lifter 21. The piston 11 is thereby pushed into its terminal inside position in its cylinder. At the same time, the spring 4 moves rocker shaft 2 to the extreme right and the valve lifter 21 of intake-valve push rod 18 is brought into engagement with the starting cam 6. Lever 8b is out of engagement with the end members 14, 15 of shaft 2.

As the engine is turned over manually or by a suitable starting motor, the pressure of the oil in the lubricating system rises. The plunger 11 moves lever 13. After a short interval in which the rotation of the engine is facilitated by the lack of compression, the lip 13a of lever 13 releases collar 17 and arm 8b moves towards collar 14 until the position of Fig. 2 is reached.

When the engine starts, the oil pressure behind plunger 11 increases further and shaft 2 is pushed to the left against the restraint of spring 4, taking valve lifters 21 along for engagement of intake-valve push rod 18 with intake cam (Fig. 3). speed of the engine is reached, shaft 9 is laterally shifted by the operator actuating lever handle 19 whereby the point of contact of lever arm 8b is shifted from collar 14 to the tip of cone 15 (Fig. 4). This causes further displacement of shaft 2 towards the left, but does not affect the operation of the cams.

In the event of failure of the oil pressure in the lubrieating system, the rocker arm 2 is moved to the right by the force of spring 4 as shown in Fig. 5 and the exhaust valve is held open by engagement of the lip 13a of lever 13 with collar 17. The lack of compression in the cylinders then stops the engine.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure, which do not constitute departure from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. A control and safety device for an internal combustion engine comprising lubricating oil pressure means, an intake valve push rod, an exhaust valve push rod, a cam shaft; intake, starting and exhaust cam means mounted .on said cam shaft, said exhaust cam means engaging said exhaust push rod for reciprocating movement of said push rod between open and closed exhaust positions; connecting means for selectively and operatively connecting said intake-valve push rod to said intake cam means and to said starting cam means; control means responsive As soon as the normal operating 1 to changes in oil pressure from said oil pressure means, for shifting said connecting means of said intake-valve push rod into and out of engagement with said intake cam means and starting cam means respectively; and locking means responsive to changes in oil pressure for locking said exhaust-valve push rod in the open exhaust position.

2. A device as set forth in claim 1, said connecting means comprising valve lifter means operatively interposed between said respective push rods and said cams, and said control means comprising rocker arm means, a rocker shaft, fixed pressure means and variable pressure means responsive to'said oil pressure, said fixed pressure means and said variable pressure means respectively urging said rocker shaft into axial movement in opposite directions, said rocker arm means being axially fixed and rotatable with respect to said rocker shaft and being fixedly connected to said valve lifter means, whereby said intake-valve push rod is selectively connected to said intake cam means at low oil pressure and to said starting cam means at high oil pressure.

3. A device as set forth in claim 2, said control means including lever means operatively interposed between said variable pressure means and said rocker shaft, a collar mounted on one end of said rocker shaft, and a cone coaxially mounted on said collar, said lever means being selectively engageable with said collar and said cone.

4. A device as set forth in claim 3, the height of said cone being substantially equal to said center-tocenter distance between said intake and said starting cam means.

5. A device as set forth in claim 1, the axial length of said exhaust cam being substantially equal to the combined axial lengths of-said intake and said starting cam.

6. A device as set forth in claim 3, said locking means being operatively connected to said lever means.

7. In an internal combustion engine including lubricat ing oil pressure means, a safety control for said engine comprising a push rod reciprocatable between an open and closed exhaust position, means for reciprocating said push rod, a collar secured to said push rod, plunger means mounted for movement in response to changes in oil pressure, resilient means biasing said plunger means against said oil pressure, said plunger means being mounted to move into the path of travel of said collar during a decrease in oil pressure and to lock said push rod into an open exhaust position.

8. In an internal combustion engine including lubricating oil pressure means, a safety control for said engine comprising a push rod reciprocatable between an open and a closed exhaust position, means for reciprocating said push rod, a collar secured to said push rod, a crank lever having an end positioned to move into and out of the path of travel of said collar, an axially adjustable plunger responsive to changes in oil pressure engageable with said lever, resilient means biasing said crank lever against said plunger whereby said end of said lever moves in response to changes in oil pressure, said lever being positioned to move into the path of said collar during decreased oil pressure and locking said push rod in its open exhaust position.

References Cited in the file of this patent UNITED STATES PATENTS 2,037,051 Smiley Apr. 14, .1936

2,191,459 Duncan Feb. 27, 1940 2,305,787 Koles Dec. 22, 1942 2,326,329 @Camp Aug. 10, 1943 2,397,511 Schreck Apr. 2, 1946 FOREIGN PATENTS 76,020 France Feb. 18, 1930 

